Need some help. 2 days ago I installed a new GPU. Had to do a fresh install of Windows as that same day the Windows update failed and I could no longer boot past the BIOS. After the fresh Windows install I was in the middle of doing all of the updates and I started hearing a grinding type noise like a HDD spinning super loud or a fan that had gears grinding sort of. I clicked shut down and my pc shut down but not fully, as everything was still on but no signal to my monitor. I held down the power button and it continued to shut off the rest of the way. Hit the power button to boot up and nothing. It would only boot if I held down the power button. Finished the updates and shut down again. Few hours later hit the power button and nothing, held it down and nothing, unplugged everything and turned off the PSU and back on, still nothing. After I removed the 24pin power connector to the motherboard it booted up fine. Ran it for a few hours and nothing out of the ordinary. Shut down fine no issues. Went to turn it back on today and same issue, only powers on after I unplug the 24pin connector. Unplugging and replugging in the 24pin connector automatically turns on the PC like the power button is stuck in a depressed position. Case is a Phanteks Eclipse p400s. All parts are 1 year old except the case which is 4 months and GPU which is 2 days old.

Admirable

Check the board header for the switch/reset etc.
Did you touch them? Has your switch on the computer failed?
You can easily test this by swapping the RESET switch on your case(if you have one) to the Power On button. So that means Power On will now be reset and vice versa.

As I was looking through everything and moving wires it looks as though I had pinched a wire when I put the back panel for the case back on. I unplugged everything, re ran my wires and plugged everything back in and also reset the CMOS and she works like a charm now. Thanks for the help.